The present invention relates to a cap with negative pressure valve, such as a fuel cap for automobiles, which is installed to an aperture of a container such as a filler neck of a fuel tank and prevents decrease of pressure in the container such as the fuel tank by flowing fluid such as air into the container from outside when the pressure in the container is decreased.
In the prior art, such cap, for example, a fuel cap for automobiles is provided with a negative pressure valve which enables flowing of air into a fuel tank so as to prevent decrease of pressure within the fuel tank.
In such cap, when the valve acts, fluid such as air inevitably passes through the valve body on account of its function. If dust is mixed in the fluid, it is liable to adhere to the valve body. In order to avoid this state, one method is that a filter cloth to cover the fluid entering flow path is arranged in the flow path at front side of the negative pressure valve. In this case, however, if the filter cloth is arranged in the fluid entering flow path so as to cover the flow path simply in plane state in orthogonal direction to the fluid entering direction, the fluid flows in and dust adheres to the filter cloth, and then even if entering of the fluid is stopped the dust may remain positioned on the filter cloth. If the dust further adheres in this state it may finally adhere throughout whole surface of the filter cloth and the fluid entering flow path be narrowed.